This invention relates to a disk subsystem composed of a disk controller and plural drive enclosures. More specifically, this invention relates to a technique which enables a disk controller to obtain drive enclosure fault information.
A disk subsystem which uses a magnetic disk drive as a storage medium is composed of a disk controller and plural drive enclosures. A Fibre Channel-arbitrated loop (FC-AL) is commonly employed to connect the disk controller and the drive enclosures with each other, thus enabling the disk subsystem to store these many drive enclosures.
FIG. 13 is a block diagram of a conventional disk subsystem.
The conventional disk subsystem is composed of a disk controller 10 and plural drive enclosures 500.
The disk controller 10 has a channel adapter 100, a disk adapter 200, a memory adapter 300, and a switch adapter 400.
The channel adapter 100 has a connection interface to connect with a host computer. The disk adapter 200 has a connection interface to connect with the drive enclosures 500. The memory adapter 300 temporarily stores data that is transferred between the host computer and the drive enclosures.
The switch adapter 400 connects DMA controllers 120, 220, and 320, which are provided in the channel adapter 100, the disk adapter 200, and the memory adapter 300, respectively, with one another to build an internal network.
The drive enclosures 500 each have plural disk drives 540. The drive enclosures 500 and the disk controller 10 are connected to each other via protocol engines 230, which are placed in the disk adapter 200, and via port bypass circuits 590, which are each in their respective drive enclosures 500.
The drive enclosures 500 are connected with one another via the port bypass circuits 590. The FC-AL connection is characterized by the port bypass circuits 590 connecting the many disk drives 540. Input ports and output ports of the disk drives 540, which are connected with one another by the FC-AL connection, are connected by a cascade connection to form one loop.
In the FC-AL connection, competition for a loop access right is arbitrated among the disk drives 540 that are connected in a loop and some of the disk drives 540 that have acquired the access right transfer data. Accordingly, an increase in number of the disk drives 540 connected raises problems concerning the data transfer bandwidth of the loop and thereby degrades the performance.
A known solution to this problem is a technique of reducing interference between the disk drives 540 upon data transfer by replacing the port bypass circuits 590 with switches (see JP 2000-222339 A, for example).